An opaque dental ceramic (porcelain) paste for applying to dental substructures, to be used in the preparation of ceramic dental appliances, such as crowns and bridges, and a method of using the same are provided.
When crowns, bridges and other metal dental substructures (copings) are to be veneered, the dental technician must first apply and fire a layer of opaque ceramic paste. This layer ensures a good bond to the veneering ceramic and, in addition, masks the unfavorable metal color of the substructure which is necessary to obtain a good aesthetic appearance.
Before the application of the opaque paste, an opaque slurry may optionally be fired on. For this purpose a thin suspension of ceramic opaque is mixed, applied and fired.
Conventional opaque ceramic paste consists of a pulverized opaque ceramic powder which is mixed with water, or a special modeling liquid, by the dental technician. The opaque powder itself consists of ground glass frits, which, owing to their chemical compositions can be melted at temperatures below 1000.degree. C. and opacifying agents. During firing, leucite is partially crystallized out, thus the thermal expansion of the glass is adapted to the thermal expansion of the metal. A high portion of opacifiers ensures a good masking of the dark metal. The opaque materials are sold in several shades since they form the color basis for the desired tooth shade.
In preparing the opaque ceramic paste, the dental technician must adjust the consistency of the paste to obtain a paste which is sufficiently viscous so as to adhere to the metal substructure without sagging, but not so viscous that it cannot be easily applied. This procedure involves much trial and error and is very time consuming.
Conventional opaque application requires much time and skill because a very even layer thickness has to be achieved. If the layer of ceramic opaque is too thin, the metal substructure shines through, when the opaque is too thick, there is not enough space left for the full application of the subsequent body and enamel layers, which results in a diminished aesthetic affect.
Accordingly, there is a need in the art for an opaque paste, and a method, which makes it possible to avoid the. time consuming procedure of mixing the paste in the laboratory, and makes it possible to apply opaque ceramic paste more easily and more consistently, using fewer steps, to dental substructures and whereby an even layer thickness is achieved.